selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/fs/ufs/Kconfig b/fs/ufs/Kconfig
new file mode 100644
index 000000000..9301e7ecd
--- /dev/null
+++ b/fs/ufs/Kconfig
@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config UFS_FS
+	tristate "UFS file system support (read only)"
+	depends on BLOCK
+	select BUFFER_HEAD
+	help
+	  BSD and derivate versions of Unix (such as SunOS, FreeBSD, NetBSD,
+	  OpenBSD and NeXTstep) use a file system called UFS. Some System V
+	  Unixes can create and mount hard disk partitions and diskettes using
+	  this file system as well. Saying Y here will allow you to read from
+	  these partitions; if you also want to write to them, say Y to the
+	  experimental "UFS file system write support", below. Please read the
+	  file <file:Documentation/admin-guide/ufs.rst> for more information.
+
+          The recently released UFS2 variant (used in FreeBSD 5.x) is
+          READ-ONLY supported.
+
+	  Note that this option is generally not needed for floppies, since a
+	  good portable way to transport files and directories between unixes
+	  (and even other operating systems) is given by the tar program ("man
+	  tar" or preferably "info tar").
+
+	  When accessing NeXTstep files, you may need to convert them from the
+	  NeXT character set to the Latin1 character set; use the program
+	  recode ("info recode") for this purpose.
+
+	  To compile the UFS file system support as a module, choose M here: the
+	  module will be called ufs.
+
+	  If you haven't heard about all of this before, it's safe to say N.
+
+config UFS_FS_WRITE
+	bool "UFS file system write support (DANGEROUS)"
+	depends on UFS_FS
+	help
+	  Say Y here if you want to try writing to UFS partitions. This is
+	  experimental, so you should back up your UFS partitions beforehand.
+
+config UFS_DEBUG
+	bool "UFS debugging"
+	depends on UFS_FS
+	help
+	  If you are experiencing any problems with the UFS filesystem, say
+	  Y here.  This will result in _many_ additional debugging messages to be
+	  written to the system log.